Hortus Botanicus Leiden, Netherlands

Common name: Japanse walnoot, Sieboldwalnoot, Japanese walnut, Heartnut, 姫胡桃 Hime-gurumi

Family: Juglandaceae (Walnut family)

Synonym: Juglans ailantifolia var. cordiformis, Juglans sieboldiana var. cordiformis

Distribution: Japan

Hardiness: Zone 04

Life form: Tree

Comments: This walnut is native to Japan and was introduced to the botanical garden by the German physician and collector Von Siebold and planted in the “nut tree field”. In a heavy storm in July 2015, the trunk was split in two and the tree had to be heavily pruned. Nevertheless, it continues to produce new leaves: a real diehard!
The twigs of this tree are dark grey in colour and have stalked glands. The leaves, which can grow up to 60-90 cm in length, are pinnate. The 11-19 leaflets that form this compound leaf are approximately 8-17 cm in length with a downy lower side. The leaf margins are serrated. The male flowers are catkins of about 8 cm long. The female inflorescences form clusters of 10-20 inflorescences. The nuts hang from long stalks and are covered by a hairy husk. They are ovate and pointed, with a thick protruding seam, and very hard. In Japan they are much valued as an edible nut.